Undocumented endpoints
Teams ship APIs without OpenAPI specs and wonder why partners take months to integrate. We deliver interactive Swagger docs, sandbox keys, and example requests from day one.
Software Engineering
APIs that power your ecosystem
Connect mobile apps, partners, and platforms with production-grade REST and GraphQL APIs — secure, documented, versioned, and built for M-Pesa, open banking, and real-world real traffic.
50K+
Peak TPS delivered
National payment APIs
4–6
Week delivery
Typical API MVP timeline
100%
OpenAPI documented
Every endpoint spec'd
v1→v2
Safe versioning
Zero breaking migrations
Integration infrastructure for modern products
Every digital product eventually becomes an API business — mobile clients, partner banks, fintech integrations, and internal microservices all depend on a reliable API layer. LesterTechLabs designs and builds API-first backends with consistent resource modeling, OAuth2 and API key auth, rate limiting, webhook delivery, and OpenAPI documentation that third-party developers can integrate against in days, not months.
Clients & partners
Mobile apps, web frontends, bank APIs, and third-party integrators
API gateway layer
Auth, rate limits, request validation, versioning, and audit logging
Application services
Django/FastAPI microservices with business logic and event publishing
Data & messaging
PostgreSQL, Redis, Kafka/webhooks, and idempotent transaction storage
POST /v1/payments/mpesa/stk-push
201 Created
{{ body|default:"{
\"status\": \"success\",
\"data\": { ... }
}" }}Challenges we solve
Common API pitfalls we see in FinTech, SaaS, and enterprise integrations — and how we engineer around them.
Breaking changes in production
Silent schema changes break mobile apps and partner systems. We implement URL or header versioning, deprecation policies, and contract tests on every release.
Payment webhook failures
M-Pesa and bank callbacks get lost, duplicated, or processed twice. We build idempotent handlers, retry queues, signature verification, and reconciliation dashboards.
Security gaps
Exposed keys, missing rate limits, and inconsistent auth across services. We apply OAuth2, scoped API keys, OWASP API Top 10 controls, and penetration-tested endpoints.
What we deliver
Core capabilities included in every api development engagement.
REST API design
Resource-oriented endpoints with pagination, filtering, consistent errors, and HATEOAS where useful.
GraphQL APIs
Flexible query layers for complex mobile and web clients with schema stitching and dataloaders.
OpenAPI & developer portals
Swagger specs, interactive explorers, sandbox environments, and partner onboarding guides.
Payment & fintech APIs
M-Pesa STK Push, Paystack, Stripe, bank transfers, and reconciliation with webhook handling.
Webhook & event systems
Reliable event delivery with retries, dead-letter queues, and signed payload verification.
API security hardening
OAuth2, JWT, API keys, rate limiting, input validation, and audit trails on every route.
Where this fits
Common scenarios we deliver this service for, in any country.
FinTech & mobile money
Payment initiation, wallet transfers, transaction status, and settlement APIs for banks and fintechs.
Mobile app backends
Auth, user profiles, push notification triggers, and offline-sync-friendly REST endpoints.
B2B partner integrations
Scoped API keys, partner sandboxes, and SLAs for ISVs connecting to your platform.
Open banking & telco
Account aggregation, KYC verification, airtime APIs, and regulated data exchange patterns.
Key benefits
- Partner-ready APIs with OAuth2, scoped keys, and documented rate limits
- OpenAPI specs and sandboxes so integrators ship in days, not months
- Versioned endpoints with backward-compatible migration paths
- Load-tested for peak traffic, slow networks, and mobile conditions
- M-Pesa, Paystack, and bank integrations with idempotent webhook processing
Why LesterTechLabs
-
Developer-First
OpenAPI specs, sandbox environments, and actionable error responses.
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Secure by Default
OAuth2, rate limiting, and validation on every endpoint from sprint one.
-
Versioned & Stable
Backward-compatible releases so partner integrations never break silently.
Our process
A proven delivery framework from kickoff to production.
-
01
API design workshop
Resource modeling, auth strategy, versioning plan, and OpenAPI draft before code.
-
02
Core implementation
Endpoints, validation, serialization, error contracts, and integration tests.
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03
Security & load testing
Pen tests, rate limit tuning, k6/Locust load tests, and staging partner UAT.
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04
Portal & handover
Developer portal, API keys, runbooks, monitoring dashboards, and optional managed support.
Technologies we use
Modern, battle-tested stacks for production workloads.
Related services
Other software engineering offerings you may need.
Frequently asked questions
Common questions about api development.
Do you build REST or GraphQL APIs?
Both. REST is our default for partner integrations, webhooks, and public APIs. GraphQL when mobile or web clients need flexible querying. We often combine both — REST for external partners, GraphQL for first-party apps.
Can you integrate M-Pesa and other payment gateways?
Yes. We build payment APIs for M-Pesa STK Push, Paybill, B2C, Paystack, Flutterwave, Stripe, and bank APIs — including webhook verification, retry logic, reconciliation jobs, and admin dashboards for failed transactions.
How do you handle API security?
OAuth2 and JWT for user-facing flows, scoped API keys for server-to-server, rate limiting per client, input validation, HTTPS everywhere, and OWASP API Security Top 10 controls. We document security requirements in every OpenAPI spec.
How long does API development take?
A focused API MVP (auth + core resources + docs) typically ships in 4–6 weeks. Full payment platforms with webhooks, admin tools, and partner portals run 8–14 weeks depending on integration count and compliance needs.
Do you provide API documentation for our partners?
Yes. Every engagement includes OpenAPI 3.x specs, Swagger UI or Redoc portals, sandbox API keys, curl/Postman collections, and onboarding guides tailored to your partner technical teams.
Can you version our API without breaking existing clients?
Yes. We implement URL versioning (/v1/, /v2/) or header-based negotiation with deprecation timelines, sunset headers, and automated contract tests that block breaking changes from reaching production.
Software Engineering
Ready to launch your API?API Development?
Share your integration goals, auth requirements, and timeline — we'll design the right API architecture and respond with a proposal within 48 hours.
- Free estimate · reply in 1 business day
- Production delivery · remote-first
- M-Pesa, cloud, and AI ready
Next step
Start your project
- 1 Tell us about your goals
- 2 Get a tailored proposal
- 3 Ship with LesterTechLabs